Here you can find the source of degToRad(angle)
function degToRad(angle) { return ((angle * Math.PI) / 180); }
Math.deg2Rad = function(deg) return (deg / 180) * Math.PI;
function degToRad(deg) { return deg * Math.PI / 180;
Math.toRadians = function(degrees){ if (degrees < 0) { degrees += 360; return degrees / 180 * Math.PI; };
Math.degrees = function(radians){ return radians * 180 / Math.PI; };
Math.radians = function(degrees){ return degrees * Math.PI / 180; };